Device for activating a security system in a vehicle

ABSTRACT

Disclosed is a device for activating a security system in a vehicle including a first and second vehicle sensor ( 4 ). The sensor include, respectively, a measuring value sensor ( 4.1 ) which can detect acceleration and structure-borne noise, and a central unit ( 2 ) which evaluates the signals of at least two vehicle sensors ( 4 ) and activates the security system according to the signals. The first and second vehicle sensors have a first direction of sensitivity for at least one measuring value sensor ( 4.1 ), which is used to detect acceleration, and a second direction of sensitivity for at least one measuring value sensor ( 4.1 ) which is used to detect structure-borne noise.

The invention relates to a device for activating a security system in avehicle according to claim 1, and a related procedure according to claim14.

Vehicle security systems require sensors to record the each driving oraccident situation in order to react in an appropriate way. It is knownthat measuring value sensors can be used as crash sensors in order torecord the acceleration and structure-borne noise. An impact with anobstacle or a collision with an obstacle is detected by the evaluationof the measured acceleration and the measured structure-borne noise, andsafety measures are initiated by the security system accordingly.Determining the origin of an impact is of great importance in order toimprove the use of security systems such as airbags, belt tighteners orpedestrian protection systems. Sensors known to date which are used torecord the structure-borne noise are designed to record preferablytransverse structure-borne noise waves. Since no one individual sensorof this type is capable of determining the direction of dissemination ofa transverse structure-borne noise wave, several sensors must be linkedin order to determine the location of the source of the structure-bornenoise wave, and in part, the evaluation of the measured structure-bornenoise values involves, in part, extensive and complex calculations.

Sensors to record the acceleration and the structure-borne noise have afurther, decisive disadvantage. Their direction of sensitivity forrecording the structure-borne noise is often not the same as thedirection of sensitivity for recording the acceleration. For thisreason, more than two sensors frequently have to be provided todetermine the impact location of the obstacle in order to guarantee thatthe security system will be activated in a manner appropriate to theaccident.

A control device for a security system is known from DE 100 15 273 A1,in which four sensors for recording the acceleration and structure-bornenoise are provided, which are arranged in such a manner that each sensorcomprises a different direction of sensitivity. In this way, it is notonly possible to determine the direction of the acceleration, but alsobe determine faults in the sensors.

The object of the present invention is to recommend a device and aprocedure for activating a security system in a vehicle which issuitable for recording acceleration and structure-borne noise.

This object is attained by means of a device for activating a securitysystem in a vehicle with the features described in claim 1, and acorresponding procedure with the features described in claim 14.Preferred embodiments of the invention result from the dependant claims.

An essential principle of the invention consists of the fact that asuitable arrangement of vehicle sensors, which is capable of recordingboth an acceleration and the vibrations within a structure-borne noisewave, the direction of sensitivity for recording an acceleration and thedirection of sensitivity for recording structure-borne noise beingaligned either differently or in the same way following modificationsmade to the structure of the vehicle sensor and to the manner in whichit is fitted. In this way, the number of vehicle sensors required, forexample to determine the impact location when a crash occurs, can beminimised.

The invention now relates to a device for activating a security systemin a vehicle with at least one vehicle sensor, which is capable ofrecording vibrations in frequency ranges which are caused by both anacceleration and by structure-borne noise, and which comprises at leastone measuring value sensor for recording vibrations and a central unit,which evaluates the signals of at least one vehicle sensor, and whichactivates the security system according to said signals. Here, at leastone vehicle sensor comprises a first direction of sensitivity of atleast one measuring value sensor for recording the acceleration, and asecond direction of sensitivity of at least one measuring value sensorfor recording the structure-borne noise. In this way, the accelerationand the structure-borne noise can be recorded in identical or differentdirections of sensitivity. In this way, the vehicle sensor can be usedin areas in which the directions of sensitivity for recording theacceleration and the structure-borne noise must necessarily beidentical, for example in order to activate a passenger protectionsystem. Equally, it can be used in areas where different directions ofsensitivity are required for recording the acceleration and thestructure-borne noise, for example in order to verify the signal from anactivation signal for a passenger protection system. Furthermore, it canbe used in vehicle diagnosis systems where a vibration analysis ofcertain vehicle elements is required.

The device preferably comprises at least a second vehicle sensor, whichdelivers signals to the central unit. When two vehicle sensors are used,a level formed from a vehicle transverse axis and a vehicle longitudinalaxis, for example, can already be monitored with regard to theacceleration and structure-borne noise, in particular the longitudinalstructure-borne noise.

In particular, the first direction of sensitivity and the seconddirection of sensitivity of the vehicle sensor can be almost identical.In this way, a vehicle sensor can record both the acceleration and thestructure-borne noise in a combined direction of coverage.

Furthermore, a direction of sensitivity of the first vehicle sensorwhich results from the first and second direction of sensitivity of thefirst vehicle sensor, and a direction of sensitivity of at least onesecond vehicle sensor which results from the first and second directionof sensitivity of at least one second vehicle sensor can be aligned at aspecified angle to each other. For example, in order to detect a crash,it is often necessary to monitor several directions in one level or inone area which relate to changes to the accelerations or structure-bornenoise of relevance to the crash.

The first and second vehicle sensor can be arranged in such a mannerthat the specified angle is almost zero.

In order to monitor with two vehicle sensors a level formed from avehicle transverse axis and a vehicle longitudinal axis with regard toacceleration and structure-borne noise, the first and at least onesecond vehicle sensor are arranged in such a manner that the specifiedangle is almost 90 degrees, the first and second direction ofsensitivity of each of the vehicle sensors deviating from each other byno more than 20 degrees.

Furthermore, the first direction of sensitivity and the second directionof sensitivity of each vehicle sensor can be aligned to each other at anangle of almost 90 degrees. Any directions of sensitivity which deviatefrom each other are required, for example, when a verification isconducted of an activation signal for a security system in a vehiclewhich has been determined on the basis of a first vehicle sensor, usinga verification signal which has been generated by a second vehiclesensor. Here, the vehicle sensors can, for example, be arranged in sucha manner that the first direction of sensitivity of the first vehiclesensor matches the second direction of sensitivity of the second vehiclesensor, and vice-versa. An activation signal which is determined fromthe acceleration of the first vehicle sensor is thus linked to averification signal which is determined from the structure-borne noiseof the second vehicle sensor, and vice-versa.

For this reason, the first and at least one second vehicle sensor can bearranged in such a manner that the first direction of sensitivity of thefirst vehicle sensor and the second direction of sensitivity of thesecond vehicle sensor of at least one second vehicle sensor are almostidentical, and vice-versa. With an arranged in this form, whereby thefirst and second direction of sensitivity of each of the vehicle sensorsdiffer by 90°, not only a level formed from the vehicle transverse axisand vehicle longitudinal axis can be monitored with regard toacceleration and structure-borne noise, but the signal verificationmentioned above can be conducted for the activation signal for asecurity system in a vehicle generated from the recorded accelerationand the recorded structure-borne noise. For example, the signal portionof a first vehicle sensor which records the acceleration can be linkedto the signal portion of a second vehicle sensor which records thestructure-borne noise, in order to generate a verified activation signalfor a security system, in particular a passenger protection system, in acentral unit. In reverse, the same signal verification is possible withthe signal portion of the second vehicle sensor which records theacceleration and the signal portion of the first vehicle sensor whichrecords the structure-borne noise.

Preferably, at least one measuring value sensor is capable of recordingthe longitudinal structure-borne noise. The advantage of recording andevaluating longitudinal structure-borne noise waves as compared totransverse structure-borne noise waves is that it is possible todetermine the source of the longitudinal structure-borne noise wave, andthus the source of the collision with an obstacle.

In particular, the device is designed to conduct a signal verificationof a signal portion of the acceleration and/or the structure-borne noiseof the first vehicle sensor with a signal portion of the accelerationand/or structure-borne noise of at least one second vehicle sensor. Itis also possible to incorporate signals from additional activationsensors in order to verify the signal.

Furthermore, the device can be design to conduct a signal verificationof the signal portion of the acceleration of the first vehicle sensorwith the signal portion of the structure-borne noise of the firstvehicle sensor.

In addition, the device can be designed to conduct a signal verificationof the signal portion of the acceleration of at least one second vehiclesensor with the signal portion of the structure-borne noise of at leastone second vehicle sensor. Each vehicle sensor thus conducts one signalverification of both of the two signal portions, which is a simpletechnical process.

The vehicle sensor can also comprise a bracket for affixing themeasuring value sensor to a vehicle element, a sensor housing, a seismicmass for recording the acceleration and the processing unit forprocessing the measuring value sensor signals, whereby at least onemeasuring value sensor is attached to the bracket via a connection.

Furthermore, at least one measuring value sensor can be attached to abracket via a tensionally locked connection, which makes it possible torecord the acceleration and/or the structure-borne noise. Thetensionally locked connection is here designed in such a manner that atransmission, for example of the longitudinal structure-borne noise, isguaranteed from a vehicle element to the measuring value sensor.

In particular, the connection for attaching the measuring value sensorto the bracket is designed in such a manner that the recording ofunwanted signals by the measuring value sensor is reduced or prevented.Since the longitudinal structure-borne noise waves comprise loweramplitudes in comparison with the transversal structure-borne noisewaves, or in comparison with the acceleration, it is advantageous whenunwanted signals are already absorbed when the connection used forattaching the bracket is made.

A low-cost way of creating an attachment connection to the bracket canto use adhesive, for example.

Furthermore, the bracket is designed, regardless of its construction, todetermine the measuring characteristics of the vehicle sensor. A vehiclesensor of this type can be varied in terms of its measuringcharacteristics during the manufacturing process or through programmingin such a way that it can be used variably for different purposes. As aresult, large number of this vehicle sensor can be produced at lowprices, for example.

Furthermore, the bracket is designed, regardless of its construction, toenable the acceleration and/or the structure-borne noise to be recorded.In particular, it enables vibration parts of the structure-borne noise,such as the longitudinal structure-borne noise, to be transmitted in aspecified direction, in order to make these available to the measuringvalue sensor. Here, the bracket can comprise a mounting element such asone used to attach a piezoelectric recorder as a measuring value sensor.The bracket can, on the other hand, also be a construction comprisingseveral mounting elements, for example when a measuring value sensordesigned as an ASIC sensor is attached to a first mounting element forbonding, is cast with a moulding mass and then attached to a circuitboard as a second mounting element.

In order to make it possible to measure longitudinal structure-bornenoise waves, for example, which comprise a comparatively low amplitude,it is also advantageous to absorb unwanted signals buy constructing thebracket in a suitable manner. For this reason, the bracket is designedto reduce, or even to prevent, unwanted measuring components from beingreceived by the measuring value sensor.

Both the bracket and the connection for attaching the measuring valuesensor to the bracket are designed to enable the longitudinalstructure-borne noise to be recorded. Recording the longitudinalstructure-borne noise is technically more complicated, since thelongitudinal structure-borne noise comprises lower amplitudes incomparison with the transverse structure-borne noise. Since incomparison with transverse structure-borne noise waves, longitudinalstructure-borne noise waves make it possible to determine the source ofthe longitudinal structure-borne noise wave, and thus the source of thecollision with an obstacle, however, the bracket and the connection forattaching the measuring value sensor to the bracket are designed in sucha manner as to make it possible to transmit the vibration parts of alongitudinal structure-borne noise wave from a vehicle element to themeasuring value sensor, while at the same time absorbing unwantedsignals.

In particular, the bracket is designed, depending on its structure, todetermine the first and second direction of sensitivity of the vehiclesensor. It is thus possible, depending on the installation site and thesetting of the vehicle sensor, to define both identical andnon-identical directions of sensitivity in order to record theacceleration and the structure-borne noise.

In particular, the bracket is designed, depending on its curvature, todetermine a first direction of sensitivity of at leas one measuringvalue sensor for recording the acceleration, and a second direction ofsensitivity of at least one measuring value sensor for recording thestructure-borne noise. If the measuring value sensor is a piezoelectricsensor, for example, the directions of sensitivity can be aligned via acurvature in the bracket in such a manner that both identical andnon-identical directions of sensitivity can be adjusted, depending onthe application site and the setting of the vehicle sensor.

In particular, the vehicle sensor can be attached within the vehiclepassenger cell or in protected hollow spaces within the vehicle if thedevice for activating a security system in a vehicle is a passengerprotection system, for example.

Furthermore, the vehicle sensors can be attached within or in the directvicinity of the central unit. Since the vehicle sensors also record thestructure-borne noise as well as the acceleration, it is not an absoluterequirement that they are attached near the outer shell of the vehicle,since the structure-borne noise waves are disseminated far more quicklyin the vehicle than the vibrations generated by changes in theacceleration, and a crash can be detected within the time necessary toactivate the security system.

When the vehicle sensors are used in a device for activating apedestrian protection system, for example, the vehicle sensors can beattached at a distance of approximately 20 centimetres from the outershell of the vehicle, for example.

If the measuring value sensor is designed as a piezoelectric sensor, oras a strain gauge, for example, the seismic mass can be adhered to atleast one measuring value sensor.

On the other hand, the seismic mass can be designed as part of themeasuring value sensor when the measuring value sensor is amicromechanical sensor, for example.

In particular, at least one measuring value sensor can be designed torecord a specific acceleration range. A specific acceleration range isspecified, depending on the installation site and the purpose of theinstallation of the vehicle sensor, which lies between +/−1 g and+/−1,000 g. If the vehicle sensor is used in the fender area of thevehicle, for example, it should record accelerations in a low rangewhich correspond to a collision with a light object and accelerations ina high range up to +/−1,000 g, which correspond to a collision withanother vehicle, for example.

On the one hand, at least one measuring value sensor can be designed tomake it possible to program a specific acceleration range. This enablesa customer-specific setting for a specific acceleration range followingafter the vehicle sensor has been produced, for example.

On the other hand, at least one measuring value sensor can be designedto make it possible to create a setting for a specific accelerationrange while the vehicle sensor is being produced. This already enables asuitable acceleration range to be defined while the vehicle sensor isbeing produced by selecting appropriate technology or an appropriatestructure.

Furthermore, the processing unit can comprise a filter for the selectiverecording of the acceleration and/or the structure-borne noise. Thisprovides a signal at the vehicle sensor exit which supplies thenecessary frequency parts of the acceleration and structure-borne noise.An external signal filter is no longer required, and reduces thecomplexity of the procedure for further evaluating the vehicle sensorsignal.

The filter in the processing unit can be programmable in order to enablethe selective recording of the acceleration and/or structure-bornenoise. In this way, customer-specific programming of the filtercharacteristics can be undertaken, in order to be able to select thesignal portions required for their specific application.

On the other hand, the filter in the processing unit can be designed insuch a manner that it can be adjusted while the vehicle sensor is beingmanufactured, in order to enable a selective recording of theacceleration and/or the structure-borne noise. In this way, the signalportions required for a specific application can already be selectedwhile the vehicle sensor is being produced.

In particular, the processing unit is designed in order to recordsignals from the measuring value sensor with a high amplitude, withoutrecording any overtravel of the amplifier circuit arranged in theprocessing unit. The amplifier circuit must be designed in such a mannerthat it is possible to record and amplify the signals from the measuringvalue sensor relating to the longitudinal structure-borne noise, forexample, which comprise lower amplitudes compared to those fromtransverse structure-borne noise, but also enabling the measuring valuesignals from the acceleration or transverse structure-borne noise withhigher amplitudes to be recorded and amplified.

At least one measuring value sensor can be a piezoelectric sensor, astrain gauge, a micromechanical sensor or a magnetic restrictive sensor.Depending on the installation site of the vehicle sensor, the vehiclesensor can be implemented in a simple, low-cost manner when a suitablemeasuring value sensor is selected. For applications in which the firstand second directions of sensitivity of the vehicle sensors must bealmost identical, the use of a micromechanical sensor is advantageous,for example, which, depending on the structure, comprises an identicalfirst and second direction of sensitivity. For applications in whichdifferent directions of sensitivity are required, it is on the otherhand advantageous to use a piezoelectric sensor, for example, with whichthe required non-identical alignment of the directions of sensitivitycan be achieved due to the curvature of the bracket.

The vehicle sensor can be designed as a moulded ASIC or as a mechatronicvehicle sensor.

Furthermore, the bracket can be designed as a Lead Frame suitable forthe moulding technique, or as a mechatronic bracket suitable for themoulding technique.

Accordingly, the sensor housing can be designed as a moulding massencompassing the bracket.

The vehicle sensor is preferably attached by pressing on or pressing inthe bracket or sensor housing within the vehicle, or within a centralunit.

Further options for using the device are for example its use indiagnosis or monitoring systems for which a vibration analysis forcertain elements is required, such as ball bearing or roller bearingmonitoring, use in systems which monitor road conditions for which avibration analysis is conducted of the vibrations which occur in thechassis, with stability and braking systems in the vehicle, or withsystems which regulate the vehicle dynamics.

The invention furthermore relates to a procedure for activating asecurity system in a vehicle with at least one vehicle sensor whichrecords vibrations in frequency ranges which are caused both by anacceleration and by structure-borne noise, and which comprises at leastone measuring value sensor to record vibrations, and a central unitwhich evaluates the sensor signals of at least one vehicle sensor andwhich activates the security system in accordance with this evaluation.At least one vehicle sensor here comprises a first direction ofsensitivity of at least one measuring value sensor for recording theacceleration, and a second direction of sensitivity of at least onemeasuring value sensor for recording the structure-borne noise.

Preferably, at least one second vehicle sensor delivers signals to thecentral unit. With two vehicle sensors, a level which is formed from thetransverse vehicle axis and the longitudinal vehicle axis, for example,can already be monitored with regard to acceleration and structure-bornenoise, in particular longitudinal structure-borne noise.

The procedure is furthermore designed to enable the acceleration and/orstructure-borne noise to be recorded using a suitable setting of thefirst and the second direction of sensitivity of at least one vehiclesensor. In this way, the acceleration and the structure-borne noise canbe recorded in identical or non-identical directions of sensitivity.

The procedure is preferably designed to enable the acceleration and/orthe longitudinal structure-borne noise to be recorded using a suitablesetting of the first and the second direction of sensitivity of at leastone vehicle sensor. The advantage of recording and evaluatinglongitudinal structure-borne noise waves as compared to transversestructure-borne noise waves is that it is possible to determine thesource of the longitudinal structure-borne noise wave, and thus thesource of the collision with an obstacle.

The procedure can also conduct a signal verification for a signalportion of the acceleration and/or the structure-borne noise from thefirst vehicle sensor with a signal portion of the acceleration and/orthe structure-borne noise from at least one second vehicle sensor.

Alternatively, or in addition to this, the procedure can also conduct asignal verification of the signal portion of the acceleration of thefirst vehicle sensor with the signal portion of the structure-bornenoise of the first vehicle sensor.

Equally, the procedure can conduct a signal verification of the signalportion of the acceleration of at least one second vehicle sensor withthe signal portion of the structure-borne noise of at least one secondvehicle sensor. In this way, each vehicle sensor conducts a signalverification of the two signal portions of the vehicle sensor, which isa simple technical process.

In order for a signal to be provided at the exit to the vehicle sensor,which delivers the required frequency parts of the acceleration and thestructure-borne noise, the procedure can be designed to selectivelyfilter the signals from the measuring value sensor.

Finally, the device according to the invention can also be used invehicle diagnosis systems.

Further advantages and potential areas of application of the presentinvention are included in the description below with reference to theexemplary embodiments shown in the drawings.

In the description, the patent claims, the summary and the drawings, theterms and reference numerals used in the list of reference numeralsappended apply.

In the drawings:

FIG. 1 shows an exemplary embodiment of a device for activating asecurity system in a vehicle according to the current art, with severalactivation sensors and a central unit

FIG. 2 shows two exemplary arrangements of acceleration sensors and acentral unit of a device for activating a security system in a vehicleaccording to the current art

FIG. 3 shows an arrangement of vehicle sensors according to theinvention and a central unit in a vehicle

FIG. 4 a shows a block diagram of the vehicle sensor

FIG. 4 b shows the filter characteristics of the processing unit of thevehicle sensor

FIG. 5 a shows a view of the vehicle sensor with a piezoelectricmeasuring value sensor, without any curvature in the bracket, and

FIG. 5 b shows a view of a vehicle sensor with a piezoelectric measuringvalue sensor with a curvature in the bracket of 90°

FIG. 6 shows a first embodiment of the device according to the patentclaims presented, with two vehicle sensors, the resulting directions ofsensitivity of which are aligned to each other at an angle of 90°, and

FIG. 7 shows a second embodiment of the device according to the patentclaims presented, with two vehicle sensors, the first direction ofsensitivity of the first vehicle sensor and the second direction ofsensitivity of the second vehicle sensor being identical, and the seconddirection of sensitivity of the first vehicle sensor and the firstdirection of sensitivity of the second vehicle sensor being identical

In the following, the application of the vehicle sensor according to theinvention as an activation sensor for a passenger protection system isexplained. However, this description should not be regarded as beinglimited to the invention, since the vehicle sensor can also be usedadvantageously for other areas of application, such as in diagnosis ormonitoring systems for which a vibration analysis of certain elements isrequired, such as ball bearing or roller bearing monitoring, in roadcondition monitoring systems for which a vibration analysis of thevibrations which occur in the chassis is conducted, and in stability andbraking systems in the vehicle or systems which regulate the vehicledynamics.

FIG. 1 shows a device for activating a security system, in particular apassenger protection system in a vehicle according to the current art,with several activation sensors 3.1, 3.2, 3.3 and a central unit 2. Thecentral unit 2 is positioned centrally in the vehicle, preferably in thecentral tunnel of the vehicle, and controls the corresponding securitysystems such as passenger protection systems or pedestrian protectionsystems.

The side sensors 3.1.2 are attached on the side in the vehicle 1 inorder to detect a side crash, and have a direction of sensitivitytowards the transverse vehicle axis. In addition, these sensors ofteninclude a direction of sensitivity towards the longitudinal vehicleaxis. This additional direction of sensitivity makes it possible, forexample, to verify a sensor output signal generated by the sensors3.1.2, in particular when accidents occur in which the effect of theforce produced during an accident or collision occurs at an obliqueangle to the longitudinal or transverse axis of the vehicle.

The sensors 3.2, 3.3 which are attached in the front section of thevehicle are used as upfront sensors to detect a frontal crash, in whichthe effect of the force occurs primarily in the direction of thelongitudinal axis of the vehicle. These sensors 3.2, 3.3 therefore havea direction of sensitivity towards the longitudinal axis of the vehicle.Here, either a single sensor 3.3 is arranged centrally in relation tothe longitudinal axis of the vehicle, or two sensors 3.2 are arrangedoutside the longitudinal axis of the vehicle in the front section, forexample in the fender.

The side sensors and upfront sensors are attached as close to the outershell of the vehicle as possible, in order to be able to detectcollisions with smaller objects as quickly as possible. Rapid detectionof an impact is particularly important in the side section of thevehicle, since here, the crusher zone is relatively small, and apassenger protection system, for example, should be activatedparticularly quickly. However, these sensors near the outer shell of thevehicle are particularly susceptible to malfunctions compared to sensorswhich must be attached inside the vehicle, such as the side sensors. Forthis reason, structure-borne noise sensors are also used to detect acrash, which are not attached so close to the outer shell of thevehicle, since structure-borne noise waves disseminate far more quicklyin the vehicle than vibrations which are generated by changes to theacceleration.

FIG. 2 shows two exemplary arrangements of acceleration sensors 3.4 anda central unit 2 of a device for activating a security system in avehicle 1 according to the current art. Using an arrangement of twoacceleration sensors 3.4, the directions of sensitivity of which arealigned at a specific angle to each other, a level created from thelongitudinal axis of the vehicle and the transverse axis of the vehiclecan be monitored with regard to changes to the acceleration which are ofrelevance to a crash. Here, the two arrangements shown in FIG. 2 arepreferably used, in which the directions of sensitivity are arranged atan angle of 90° to each other. In the first arrangement, the directionof sensitivity of the first acceleration sensor is aligned in parallelto the longitudinal axis of the vehicle, and the direction ofsensitivity of the second acceleration sensor is aligned towards thetransverse axis of the vehicle. In the second arrangement, thedirections of sensitivity of the two acceleration sensors are offset at+/−45° to the long axis of the vehicle.

FIG. 3 shows an arrangement of vehicle sensors 4 in accordance with thepresent claims and a central unit 2 in a vehicle. Since these vehiclesensors 4 record the structure-borne noise as well as the acceleration,it is not necessary to attach them near the outer shell of the vehicle,since the structure-borne noise waves disseminate far more quickly inthe vehicle than the vibrations which are generated by changes to theacceleration, and a crash can be detected within the time necessary toactivate the security system. With the arrangement of two vehiclesensors shown, a level created from the longitudinal axis of the vehicleand the transverse axis of the vehicle can be monitored with regard tostructure-borne noise and changes to the acceleration which are ofrelevance to a crash.

Furthermore, it is possible to conduct a signal verification of therelevant sensor output signals from the vehicle sensors 4, wherebyeither the sensor output signal of the first vehicle sensor 4 isverified with the sensor output signal of the second vehicle sensor 4,or the signal portion of the vehicle sensor which transmits theacceleration, for example, is verified with the signal portion of thesame vehicle sensor 4 which transmits the structure-borne noise. Inaddition, sensor output signals from other vehicle sensors 4 attached inthe vehicle used for signal verification purposes.

Since the vehicle sensor 4 can be attached at different locations in thevehicle, where lower or higher accelerations can be measured dependingon the accident situation, a specific acceleration range can bespecified in relation to the application of the vehicle sensor 4 duringthe manufacturing process, which lies between +/−1 g and +/−1,000 g. Ifthe vehicle sensor is installed in the fender section of a vehicle, forexample, it should record accelerations in a low range, which occurfollowing a collision with a light object, and acceleration in a highrange up to +/−1,000 g which may for example occur following a collisionwith another vehicle. The acceleration range should be selected in sucha manner that the vehicle sensor 4 measures the necessary accelerationson the one hand, in order to detect and accident, while on the otheravoiding an overtravel in the processing unit when processing thesignals from the measuring value sensor. Alternatively, the vehiclesensor can be designed in such a manner that the acceleration range canbe programmed in a customer-specific way, depending on the way in whichthe vehicle sensor is to be used.

The processing unit 4.2 of the vehicle sensor comprises an amplifyingcircuit which amplifies the different signal portions which transmit themeasured acceleration and structure-borne noise. In particular, theprocessing unit 4.2 is design to record signals from the measuring valuesensor with a high amplitude, without an overtravel of the amplifyingcircuit. The amplifying circuit records and amplifies signals from themeasuring value sensor from the longitudinal structure-borne noise, forexample, which comprise lower amplitudes than those of transversestructure-borne noise, but also measuring value signals from thetransverse structure-borne noise with higher amplitudes.

In order to provide a signal at the exit of the vehicle sensor, whichdelivers the required frequency parts of the acceleration and thestructure-borne noise, the processing unit 4.2 comprises a filter toselectively record the acceleration and the structure-borne noise. Anexternal signal filter is then no longer required, and reduces thecomplexity involved in a further evaluation of the signal from thevehicle sensor. The filter in the processing unit 4.2 can beprogrammable to enable the filter characteristics to be programmed in acustomer-specific way, and to enable the customer to select the signalportions required for a specific application. Alternatively, the filterin the processing unit 4.2 can be designed in such a manner that it canbe adjusted during the manufacturing process of the vehicle sensor. Inthis way, the signal portions required for a specific application canalready be selected while the vehicle sensor is being produced.

Incidentally, the vehicle sensor 4 can be also be used for purposesother than crash detection. Further options for use are its use indiagnosis or monitoring systems, for example, in which a vibrationanalysis is required for certain elements, such as in ball bearing orroller bearing monitoring systems, use in systems which monitor roadconditions, for which a vibration analysis is conducted of thevibrations which occur in the chassis, with stability and brakingsystems in the vehicle, or with systems which regulate the vehicledynamics. Here, the vehicle sensors monitor the movements in a system.The directions of sensitivity of the acceleration and thestructure-borne noise are specified by the application and are definedby the structure of the vehicle sensor while the vehicle sensor is beingmanufactured.

FIG. 4 a shows a block diagram of the vehicle sensor 4 which comprises ameasuring value sensor 4.1 for recording the acceleration andstructure-borne noise, and a processing unit 4.2 for processing thesignals from the measuring value sensor. The processing unit 4.2contains a filter for selectively recording the acceleration and thestructure-borne noise. In this way, a sensor output signal 4.5 isprovided which delivers the required frequency parts of the accelerationand the structure-borne noise. Since the longitudinal structure-bornenoise waves comprise lower amplitudes compared to the transversestructure-borne noise waves, or compared to the acceleration, anamplifying circuit is provided accordingly, which makes it possible toprocess the longitudinal structure-borne noise waves. The processingunit 4.2 can also contain an A/D converter, which provides the sensoroutput signal 4.5 in digital form. The sensor output signal 4.5 is thenprocessed in analogue or digital form by an evaluation unit 2.1 in thecentral unit 2, in order to generate an activation signal for ass, suchas a passenger protection system.

FIG. 4 b shows the corresponding filter characteristics of theprocessing unit 4.2 of the vehicle sensor 4 from FIG. 4 a, in which thefrequency parts of the acceleration in the lower frequency range (lowerthan approx. 500 Hz) and the frequency parts of the structure-bornenoise in the upper frequency range (higher than approx. 4 kHz) arerecorded.

FIG. 5 a contains a view of a vehicle sensor 4 with a piezoelectricmeasuring value sensor without a curvature of the bracket 4.3. Thevehicle sensor 4 is attached to a vehicle element 5, preferably bypressing in or pressing on the bracket 4.3 within or close to thecentral unit or close to the outer shell of the vehicle. The measuringvalue sensor 4.1 is preferably attached via a tensionally lockedconnection, such as an adhesive connection, to the bracket 4.3. Thetensionally locked connection is designed in such a manner that itenables the acceleration and the structure-borne noise which affect thelongitudinal direction to be recorded on the one hand, while on theother, reducing unwanted signals, or preventing them from being recordedby the measuring value sensor. A seismic mass 4.4 which is required formeasuring any accelerations which occur is directly attached to themeasuring value sensor 4.1, preferably using adhesive.

Alternatively, the seismic mass 4.4 is also integrated in the measuringvalue sensor 4.1. If the measuring value sensor 4.1 is a micromechanicalsensor, for example, comb structures are provided for recording theaccelerations, whose movement against each other represents ameasurement of the acceleration. In this case, the seismic mass 4.4 is amovable comb structure which moves against firmly attached combstructures.

If a collision occurs in the direction of impact 6, for example when acrash occurs, the longitudinal structure-borne noise waves disseminatein the same direction 6.1 as the direction of impact 6. The direction ofdissemination of the transverse structure-borne noise waves 6.2 is,however, vertical to the direction of impact 6. The longitudinalstructure-borne noise waves are transferred via the bracket 4.3 to themeasuring value sensor 4.1, whereby the direction of dissemination ofthe longitudinal structure-borne noise waves 6.1.1 transferred onto thebracket 4.3 and that of the longitudinal structure-borne noise waves6.1.2 recorded in the measuring value sensor 4.1 runs parallel to thedirection of impact and the original direction of dissemination of thelongitudinal structure-borne noise wave 6.1 transferred in the vehicleelement.

Due to the construction of the vehicle sensor 4 with the seismic mass4.4 which is directly attached to the measuring value sensor 4.1, anacceleration of the measuring value sensor 4.1 is detected, whichcomprises a direction of dissemination 6.3 which runs vertically to thedirection of dissemination of the longitudinal structure-borne noisewave. The first direction of sensitivity of the measuring value sensor4.1 for recording the acceleration 6.3 is therefore not identical to thesecond direction of sensitivity of the measuring value sensor 4.1 forrecording the longitudinal structure-borne noise waves 6.1.2.

In order to achieve an identical direction of sensitivity for recordingboth the acceleration and the longitudinal structure-borne noise waves,the longitudinal structure-borne noise waves are deflected, as shown inFIG. 5 b, by a curvature in the bracket 4.3, so that the measuring valuesensor 4.1 is fed the structure-borne noise waves 6.1.2 which run in thealtered direction of dissemination, whereby the direction ofdissemination of the acceleration 6.3 is the same as the direction ofdissemination of the longitudinal structure-borne noise waves 6.1. Thecurvature of the bracket 4.6 is completed in such a manner that thedirection of dissemination of the longitudinal structure-borne noisewaves 6.1.2 is altered by 90°, but that preferably, reflection waves areprevented from being generated.

Generally, it is possible to adjust each direction of sensitivityrequired for recording the acceleration and the longitudinalstructure-borne noise by selecting a suitable angle in the curvature ofthe bracket 4.6. Preferably, an angle is selected which sets the firstand the second direction of sensitivity as being identical, taking intoaccount the direction of sensitivity of the seismic mass 4.4.

If the measuring value sensor 4.1 designed as a flexible piezoelectricsensor, for example, it can no longer be attached to a straight sectionof the bracket 4.3, but also extends, as shown by the dotted line, overthe area of curvature of the bracket 4.3. Further embodiments of theinvention of the measuring value sensor 4.1 can be strain gauges,magnetic restrictive sensors of micromechanical sensors.

The bracket 4.3 is designed in such a manner that it enables theacceleration and the structure-borne noise which affect the longitudinaldirection to be recorded on the one hand, while on the other, reducingunwanted signals, or preventing them from being transmitted to themeasuring value sensor 4.1. The bracket is preferably designed as a LeadFrame suitable for the moulding technique, or as mechatronic bracketsuitable for the moulding technique. A moulding mass which encompassesthe bracket serves as a sensor housing.

FIG. 6 shows a first embodiment of the device in accordance with thepresent patent claims in a vehicle 1 with a central unit 2 and twovehicle sensors 4, whose resulting directions of sensitivity 7.3 arealigned at an angle of 90° to each other. Here, the first direction ofsensitivity 7.1 and the second direction of sensitivity 7.2 of therelevant vehicle sensor 4 are aligned identically or nearly identically,the first or second sensitivity axis deviating from the resultingsensitivity axis by no more than +/−20°.

With this arrangement, the level created from the longitudinal axis ofthe vehicle and the transverse axis of the vehicle can be monitored withregard to structure-borne noise and changes to the acceleration whichare relevant to a crash.

By contrast, FIG. 7 shows a second embodiment of the device inaccordance with the present patent claims in a vehicle 1 with a centralunit 2 and two vehicle sensors 4, whereby the first direction ofsensitivity 7.1 of the first vehicle sensor 4 and the second directionof sensitivity 7.2 of the second vehicle sensor 4 are identical, and thesecond direction of sensitivity 7.2 of the first vehicle sensor and thefirst direction of sensitivity 7.1 of the second vehicle sensor areidentical.

With arrangements of this type, in which the first direction ofsensitivity 7.1 and the second direction of sensitivity 7.2 are aligneddifferently, the signal portion of the first vehicle sensor 4 whichtransmits the acceleration can, for example, be linked to the signalportion of the second vehicle sensor 4 which transmits the longitudinalstructure-borne noise, in order to generate a verified activation signalfor a security system, in particular a passenger protection system. Inreverse, the same signal verification is possible with the signalportion of the second vehicle sensor which transmits the accelerationand the signal portion of the first vehicle sensor which transmits thelongitudinal structure-borne noise.

Should additional vehicle sensors 4 be arranged in the vehicle, a signalverification is also possible with signal portions of these vehiclesensors, whereby in each case, a signal portion of one vehicle sensorwhich transmits the acceleration is linked to a signal portion ofanother vehicle sensor 4 which transmits the longitudinalstructure-borne noise.

Depending on the number of links between the individual signal portionsand the alignment of the directions of sensitivity of the relevantvehicle sensors 4, s verifications can be conducted at different levelsof complexity.

LIST OF REFERENCE NUMERALS

-   1 Vehicle-   2 Central unit-   2.1 Evaluation unit in the central unit-   3.1.2 Side sensors with directions of sensitivity in the transverse    and longitudinal axes of the vehicle-   3.2 Upfront sensors arranged in pairs-   3.3 Individual upfront sensor arranged centrally-   3.4 Acceleration sensor-   4 Vehicle sensor for recording an acceleration an structure-borne    noise-   4.1 Measuring value sensor-   4.2 Processing unit-   4.3 Bracket-   4.4 Seismic mass-   4.5 Sensor output signal-   4.6 Curvature of the bracket-   5 Vehicle element-   5.1 Spectral portions of the acceleration-   5.2 Spectral portions of the structure-borne noise-   5.3 Acceleration-   5.4 Structure-borne noise-   5.5 Activation signal for a security system in a vehicle-   6 Direction of impact-   6.1 Direction of dissemination of the longitudinal structure-borne    noise wave-   6.1.1 Direction of dissemination of the longitudinal structure-borne    noise wave transmitted onto the bracket 4.3-   6.1.2 Direction of dissemination of the longitudinal structure-borne    noise wave recorded in the measuring value sensor-   6.2 Direction of dissemination of the transverse structure borne    noise wave-   6.3 Direction of dissemination of the acceleration-   7.1 First direction of sensitivity of the acceleration-   7.2 Second direction of sensitivity of the longitudinal    structure-borne noise wave-   7.3 Resulting direction of sensitivity of the vehicle sensor

1. A device for activating a security system in a vehicle with at leasttwo vehicle sensors (4), each of which can record vibrations infrequency ranges, which are generated both by an acceleration and bystructure-borne noise, and which comprise in each case at least onemeasuring value sensor (4.1) for recording vibrations, and a centralunit (2) which evaluates the signals from the vehicle sensors (4), andwhich activates the security system according to said signals,characterised in that in each case, the vehicle sensors a) comprise afirst sensitivity direction (7.1) of at least one measuring value sensor(4.1) for recording the acceleration, and b) a second direction ofsensitivity (7.2) of at least one measuring value sensor (4.1) forrecording the structure-borne noise c) the first direction ofsensitivity (7.1) and the second direction of sensitivity (7.2) of eachvehicle sensor (4) are aligned to each other at an angle of almost 90degrees d) whereby the vehicle sensors are arranged in relation to eachother in such a manner that the first sensitivity direction (7.1) of thefirst vehicle sensor and the second sensitivity direction (7.2) of thesecond vehicle sensor, and the second sensitivity direction (7.1) of thefirst vehicle sensor and the first direction of sensitivity (7.2) of thesecond vehicle sensor are almost identical.
 2. A device according toclaim 1, characterised in that it is designed to conduct a signalverification of a first signal portion of the acceleration and/or of thestructure-borne noise of the first vehicle sensor (4) with a signalportion of the acceleration and/or the structure-borne noise of at leastone second vehicle sensor (4).
 3. A device according to claim 2,characterised in that an activation signal determined from theacceleration from the first vehicle sensor is linked with a verificationsignal determined from the structure-borne noise from the second vehiclesensor, and an activation signal determined from the acceleration fromthe second vehicle sensor is linked with a verification signaldetermined from the structure-borne noise from the first vehicle sensor.4. A device according to any one of the above claims, characterised inthat at least one measuring value sensor (4.1) records the longitudinalstructure-borne noise.
 5. A device according to any one of the aboveclaims, characterised in that at least one measuring value sensor (4.1)is designed to enable a specific acceleration range to be programmed. 6.A device according to claim 5, characterised in that at least onemeasuring value sensor (4.1) is designed to enable a specificacceleration range to be set during the manufacturing process of thevehicle sensor (4).
 7. A device according to any one of the aboveclaims, characterised in that the processing unit (4.2) comprises afilter for the selective recording of the acceleration and/or thestructure-borne noise.
 8. A device according to claim 7, characterisedin that the filter in the processing unit (4.2) can be programmed, inorder to enable the acceleration and/or the structure-borne noise to berecorded selectively.
 9. A device according to claim 8, characterised inthat the filter in the processing unit (4.2) can be adjusted during themanufacturing process of the vehicle sensor (4), in order to enable theacceleration and/or the structure-borne noise to be recordedselectively.
 10. A device according to any one of the above claims,characterised in that the processing unit (4.2) is designed to recordthe signals from the measuring value sensor with a high amplitude,without overtravelling an amplifying circuit arranged in the processingunit (4.2).
 11. A device according to any one of the above claims,characterised in that at least one measuring value sensor (4.1) is apiezoelectric sensor, a strain gauge, a micromechanical sensor or amagnetic restrictive sensor.
 12. A procedure for activating a securitysystem in a vehicle with at least two vehicle sensors (4), which recordthe vibrations in frequency ranges which are generated both by anacceleration and by structure-borne noise, and which comprises in eachcase at least one measuring value sensor (4.1) to record vibrations, anda central unit (2) which evaluates the sensor signals from the vehiclesignals, and which activates the security system according to saidsignals, characterised in that in each case, the vehicle sensors a) afirst direction of sensitivity (7.1) of at least one measuring valuesensor (4.1) for recording the acceleration, and b) a second directionof sensitivity (7.2) of at leas one measuring value sensor (4.1) forrecording the structure-borne noise c) the first direction ofsensitivity (7.1) and the second direction of sensitivity (7.2) of eachvehicle sensor (4) are aligned to each other at an angle of almost 90degrees d) whereby the vehicle sensors are arranged in relation to eachother in such a manner that the first direction of sensitivity (7.1) ofthe first vehicle sensor and the second direction of sensitivity (7.2)of the second vehicle sensor are almost identical.
 13. A procedureaccording to claim 12, characterised in that a signal verification of asignal portion of the acceleration and/or the structure-borne noise fromthe first vehicle sensor (4) is conducted with a signal portion of theacceleration and/or the structure-borne noise of at least one secondvehicle sensor (4).
 14. A procedure according to claim 13, characterisedin that an activation signal determined from the acceleration from thefirst vehicle sensor is linked with a verification signal determinedfrom the structure-borne noise from the second vehicle sensor, and anactivation signal determined from the acceleration from the secondvehicle sensor is linked with a verification signal determined from thestructure-borne sound from the first vehicle sensor.